1. Field of the Invention
The present invention relates to an active matrix display device using a plastic substrate and method of fabricating the same.
2. Discussion of Related Art
FIG. 1 is a cross-sectional view of a conventional active matrix display device. Referring to FIG. 1, the conventional active matrix display device is a device that displays a unit image of a predetermined display and includes a thin film transistor (TFT), a capacitor (C), and an organic light emitting diode (OLED). Here, the TFT is formed on a buffer layer 3a in a first region of a substrate 1a, and the capacitor C is formed on an interlayer dielectric layer 15a in a second region of the substrate 1a. 
In the above-described conventional active matrix display device, an activated active region can be defined in the TFT using lithography equipment, in the case of using a glass substrate. However, in the case of using a plastic substrate, it is impossible to define the activated region in the TFT using the lithography equipment because the plastic substrate is deformed. If the activated region is disposed adjacent to a gate, an excessive leakage current occurs from the TFT so that the OLED cannot operate.
Also, during a low temperature activation process using a laser, the glass substrate passes the laser and avoids being deformed, whereas the plastic substrate absorbs the laser and suffers from thermal deformation.
To prevent the thermal deformation of the plastic substrate, some manufacturers may adopt a process operation of etching an active region after an activation process using a laser. However, in this case, a leakage current occurs between devices through a gate terminal, so that the OLED cannot operate.
Further, since the plastic substrate requires a sufficient alignment margin in comparison to the glass substrate, the area of the capacitor C in the unit pixel is greatly increased and an aperture ratio is notably reduced. Therefore, the conventional active matrix display device needs to form a large-sized capacitor in a small area.